The carriage of objects by human beings is among the oldest of the arts. Classically the support of the weight being carried has involved the use of the upper torso, and even also the neck and head as a columnar support for the load. Carriage of objects such as baskets balanced on the head is an ancient example. Carriage with a beam or pole balanced on the shoulder is another ancient example.
Such arrangements are for simpler tasks such as the freighting of objects from one place to another, over relatively regular ground, and with no concurrent need for vigorous other activities. They are not suitable, for example, for soldiers or hikers who must change their postures and gait while still carrying their load. For this purpose there have been developed numerous pack systems, principally to be worn on the back, and with few exceptions to be supported principally on the shoulders. Again, the upper torso is utilized as a supporting column, along with the hips and legs, of course.
The human spine is notoriously subject to strain and damage. Excessive loads, especially those exerted in an eccentric manner, can and do damage the spinal discs. Tilting forces can and do cause disabling strain. In every situation, the need to balance or to lean against the load in such a way as to use the upper torso as a column, and especially to exert restoring forces that keep it and its load in a stabilized condition, is very tiring. An exhausted soldier cannot fight as well. An exhausted hiker cannot fully enjoy the scenery or hike as far.
One mitigating technique is to lighten the payload. For this reason, lightweight dehydrated foods have been prepared. Another is to lighten the pack structure itself. These techniques have inherent limitations. For example some missions require the carriage of sufficient supplies for a soldier to remain independent for a substantial period of time, and lightening the load is impossible. In fact, the available load that can be carried is frequently a limitation on a mission. Lightening the structure of presently-known packs is also inherently limited. The structure still must be strong enough to carry the load and withstand random forces without collapse. The use of lightweight materials and of special cross-sections are routinely resorted to. Still it remains an objective to increase the load which can be carried and to decrease the weight of the structure. An even more important, but heretofore unattained objective is markedly to reduce or preferably to eliminate the stressful forces on the wearer which he must resist when his upper torso is used as a column.
One effort to increase the attainable load provides a wearable vest-like garment, over which the load, such as rounds of ammunition, is distributed. This distribution assists in balancing the load, but the load is still carried by the torso, generally being transferred to the shoulders, or perhaps in part to the torso itself by closely fitting the garment to the shoulders and to the torso. While this arrangement is an improvement over an A-frame for some applications, it is far from a general or optimum solution to the problems.
In U.S. Pat. No. 4,561,578 issued Dec. 31, 1985, to the instant applicant, there is disclosed a pack frame which is supportable at least in part at the waist by an encircling belt. The pack includes a frame mounted to the belt, some over-the-shoulder stabilizing (and usually some load-supporting) straps, and counterweight means to assist in balancing the load. Containers for articles are attached to the frame. Thus, although much or even most of the load is supported at the waist, the upper torso is at least partially used as a supporting column. The human skeleton is much more efficient for supporting load by the hips and legs than by the upper torso. The patented framework has many advantages and has proved its usefulness for many purposes, especially for those of a more recreational nature where attainment of maximum loads and optimal facility of maneuver are not of greatest concern. For example, a soldier who must run or crawl with it, or jump from an aircraft with it, will continue to wish for improvements. The instant invention provides them.